1. Technical Field
The present invention relates to an exhaust gas treatment apparatus.
2. Background Art
The applicant has developed a liquid column absorption tower, in which an absorbing solution is sprayed (injected) upward to clean exhaust gas, as an absorbing device for cleaning exhaust gas in wet type exhaust gas desulfurization equipment, and this liquid column absorption tower has been used practically (Japanese Utility Model Provisional Publication No. 59-053828). In the liquid column absorption tower, a liquid column is formed by spraying (injecting) the absorbing solution upward from a spray header.
The absorbing solution, which is injected from the spray header and sprayed upward, disperses in a top portion, and then falls. The falling absorbing solution and sprayed-up absorbing solution collide with each other to form fine particles. Therefore, the gas-liquid contact area per unit volume increases as compared with a packed absorption tower. Also, the absorbing solution disperses and exists in a particulate form, and further exhaust gas is effectively entangled with the blowup flow of absorbing solution in the vicinity of a nozzle, so that the absorbing solution and exhaust gas are effectively mixed with each other, and hence the gas-liquid contact efficiency is increased. Therefore, due to these effects, the volume of an absorption tower can be comparatively small. Also, unlike a packed absorption tower, there is no need for a packing material to be cleaned and replaced. Further, since the liquid column absorption tower has no moving parts, there is no need for maintenance, and therefore an operator skilled in operation is not needed. Still further, a liquid column absorption tower has the advantage that the pressure loss of exhaust gas in the absorption tower is low as compared with a packed absorption tower.
For the absorption tower in which exhaust gas flows in the direction opposite to that which falling liquid drops, exhaust gas is introduced into the absorption tower from the lower side surface thereof. Because of the restriction of absorption tower arrangement, the construction is such that the flow of the introduced gas suddenly changes from a direction horizontal to the absorption tower to a vertical direction at this time.
It is known that the residence time of liquid drops increases as the flow velocity of exhaust gas increases, and the gas-side mass transfer resistance decreases, so that the absorbing performance is improved. However, this phenomenon is limited to the case of ideal gas flow (straightened and uniform gas flow without gas drift). In practice, if the flow velocity of exhaust gas is increased, the liquid drops disperse unevenly, and channeling (blowing through) is produced locally by the gas drift in the absorption tower, by which the absorbing performance is sometimes degraded. This problem is liable to arise especially when the size of absorption tower is increased.